1. Field of the Invention
The present invention relates to an instant camera and a manufacturing method of the same. More particularly, the present invention relates to an instant camera in which processing solution in an instant film unit can be spread in reliable fashion, and a manufacturing method of the instant camera.
2. Description Related to the Prior Art
In an instant camera, film units of a self-processing type, called "instant film", are used. These can be peel-apart type film units or mono-sheet type film units. In an instant camera for use with film units of the mono-sheet type, the depression of a release button for taking a photograph operates a shutter device. The film unit is squeezed between, and advanced by, spreading rollers. A processing solution pod provided at the front end of the unit is ruptured. The processing solution pressed out of the solution pod is spread with a uniform thickness between photo-sensitive and image-receiving sheets, while the film unit passes between the spreading rollers. After the film unit is ejected from the instant camera, a photographic image gradually forms on the image-receiving sheet.
For such a camera to take an instant photograph of a reliable quality, it is necessary to coat a photo-sensitive surface with processing solution in uniform fashion. In view of this, it is important to minimize minute deviation in diameter of the spreading rollers with precision. Conventionally rigid steel has been used for forming spreading rollers for high precision in size.
For reliable application of stable pressure to a film unit passed between spreading rollers, there is a proposal in that one of the two rollers is constructed as stationary, and another movable. One end shaft at an end of the movable roller, to be held rotatably, is pressed toward the stationary roller constantly by a spring. The confronted pair of the end shafts of the movable and stationary rollers are kept closer. The centers of the rollers are movable away from one another, as well as the film unit during passage can be squeezed by the bias of the spring.
However the steel rollers are excessively difficult to manufacture with high efficiency. To smooth the passage of film units, surfaces of the rollers requires finishing through a sandblasting process to heighten friction. To avoid rust on the steel surfaces, rollers requires plating. Such processes raise expenses in the manufacture to a great extent, as well as the construction of the spreading rollers is inconsistent with mass production. Besides, the use of the steel material raises the weight of the instant camera, and lowers portability of the camera.
It is conceivable to form spreading rollers from plastic material. However, the plastic rollers have remarkable resiliency. It has been found that the rollers are deformed outward if pressed toward one another by the above-mentioned spring associated with end shafts of the rollers. This is conspicuous particularly in the course of squeezing a solution pod in the film unit in passage. The processing solution cannot be spread without irregularity on the entirety of the photo-sensitive surface of the film unit. An image quality of the film unit will be degraded when finished. Another measure to reduce deformation of spreading rollers could be to enlarge a diameter of each roller. However, this could enlarge a size of an instant camera to an unwanted extent.